Edit: I stand corrected; there is reportedly no true Indian dna available bc they were smart and never participated in these data mining stunts. This test wasn’t a pure embellishment based on pure conjecture. It’s like substituting alligator bones for raptor fossils in your backyard
It wasn't that they were smart, there is another reason they don't participate in DNA testing. If they were to be tested, a large amount of the "indians" would be found to not qualify for tribal status.
The other (unspoken) reason is, within many of the large Indian Reservations, a culture of "stay within the tribe" exists. To the point, that many tribes are so inbred, it would shock them to realize that as a people, they're only about 4-5 generations away from extinction.
How does this happen you ask? Ever seen an annual "tribal gathering"? There's an unspoken rule during the 3-7 day gathering, where alcohol and drugs abound, that no one is really married, and 15yr old girls are often targeted for being "broken in". Sure enough, 9 months after a tribal gathering, a much higher than normal amount of children are born, often with the father listed as "unknown". It's not uncommon at all for these young girls to be raped/broken in by uncles and cousins, and so the in breeding continues (and BIA looks the other way).
It's also the reason BIA police almost NEVER use DNA testing as evidence in a crime...because it can't prove anything (everyone is related, so the DNA evidence would be inconclusive) and it would just open a big can of worms.